1. Field of the Invention
The present invention relates to an electrode disposed on a substrate, an electron emission element having a fibrous electron emission member disposed on the electrode, an electron source having a plurality of the electron emission elements, an image display device including the electron source, and a method of manufacturing the same.
2. Description of the Related Art
In recent years, there has been suggested a panel image display device with electron emission elements such as, for example, field emission elements (FE elements), metal-insulator-metal elements (MIM elements), or surface conduction electron emission elements (SCE elements).
This image display device includes, for example, an electron source having a plurality of matrix-driven electron emission elements formed on an electrically insulative substrate and an opposing image forming member for displaying an image by irradiation with electron beams. Thus, it generates a light-emitting image by applying a high voltage to the image display member to accelerate electrons emitted from the electron emission elements so as to cause the electrons to be incident on the image forming member such as a fluorescent substance.
If the high voltage is applied to the image display member, an electric potential is generated on the insulated surface region around the electron emission elements which counter an anode due to X-ray and charged ion irradiation. The higher the impedance of the substrate is, the longer the time constant of the electric potential is, and therefore a charged condition remains as it is. Furthermore, an emission of electrons from the electron emission elements in this condition causes the electrons to collide with the charged substrate surface. At that time, if the acceleration of the electrons causes charged particles such as electrons or ions to be implanted into the substrate surface, secondary electrons are generated, and particularly under a high electric field, abnormal discharge will occur. Therefore, it significantly deteriorates the electron emission characteristic of the electron emission elements, and in the worst case the electron emission elements may be destroyed, as is experimentally verified.
Conventionally, for preventing the above abnormal discharge in the image display device with the SCE elements, there is a known method of forming a high-resistant conductive film as an antistatic film by vacuum deposition or sputter deposition or of forming an antistatic film by spraying a solution containing an antistatic material (refer to, for example, Japanese Laid-Open Patent Publication (Kokai) No. 2002-358874).
If the formation of the antistatic film is applied particularly to an electron emission element that has an electron emission unit made of a fibrous material assembly among the electron emission elements, however, there is a problem that the fibrous material is stained at the formation of the antistatic film and thus the electron emission characteristic deteriorates, thereby increasing color drift, uneven luminance, or a feeling of noise caused by fluctuations. Furthermore, particularly in the formation of the antistatic film by spraying the solution containing the antistatic material, a capillary phenomenon easily causes the solution to be caught into the fibrous material formation region. It then leads to a problem that the electron emission element is susceptible to a deterioration in the electron emission characteristic (VI characteristic) caused by bending or a collapse of the fibrous material due to an adhesion of the solution, an occurrence of an uneven formation of the antistatic film caused by the solution around the fibrous material formation region caught into the region, and excessive dirt of the fibrous material.